With the utilization of rotational retorts or the like, some securing means is generally required to secure the baskets situated therein to prevent shifting of the basket within the retort during rotation.
Ideally, a loaded basket should be able to be placed into the retort and rotated during treatment (or otherwise moved) in a series of smoothly executed movements without undue jarring or uncontrolled contact.
Even a small movement between the basket and the retort (or rotational insert where one is used) results in continuous wear and tear on the basket and retort, strain on the drive system due to inconsistent forces associated with the movement of the basket(s) (each loaded basket can weigh in excess of 4000 lbs), and potential damage to the product situated within the baskets.
Prior art patents such as U.S. Pat. No. 5,676,047 entitled “Rotating Variable Height Clamping Device” issued Oct. 14, 1997 is an example of a clamping mechanism formed to engage and clamp a stack loaded into the retort. A moveable “top member” is provided to be raised and lowered to engage the stack. However, such mechanical configurations are expensive to provide and maintain, and are prone to breakage due to the extreme operating environment caused by high temperatures under pressurized conditions, high operating cycles and high weights associated with the stack. Further, the nature of the actuator requires that it be fabricated of expensive materials due to the extreme operating environment.
Further, the prior art actuators are required to be operable on a rotating mechanism, which further complicates its design and propensity for breakdown. In the '047 device, the stack is secured via actuators at the top and bottom of the stack only; accordingly, there remains clearance at the sides of the basket, which can result in slippage and shifting of the stack and its contents.
Typically, air cylinders were employed in prior systems, so as to actuate plates located above the baskets in the insert, clamping against opposing small bearing transfer rollers. This design had a tendancy to put a point load on the center of the basket, which provides uneven pressure accross the basket. It is believed that no side actuators where provided, so generally the product shifted slightly during the treatment process.
Another shortcoming of the prior art actuators is they provided only point to point contact with the baskets, providing pressure to only a portion of the basket, resulting in uneven pressure, which not only stresses the basket, but also increases the likelihood of movement of the basket even when clamped, thereby resulting in shifting of the materials which further stresses the basket structure and rotational insert, as well as rotational drive mechanism, while potentially damaging the materials therein.
There is accordingly a need in the industry for a system for providing a secure clamping arrangement to loaded baskets within a retort which is reliable in operation, relatively cost effective to implement and maintain, and which can handle the extreme operating environment and high duty cycle of an industrial retort operation.